Overactive bladder (OAB) is characterized by urinary urgency with or without urge urinary incontinence, usually with frequency and nocturia, in the absence of urinary tract infection or other obvious pathology. Antimuscarinic agents such as solifenacin are commonly used but may provide incomplete symptom control. Tadalafil (a Phosphodiesterase type 5 inhibitorsinhibitor) has been reported to improve lower urinary tract symptoms and may offer additional benefit in overactive bladder. This randomized controlled trial evaluates the efficacy and tolerability of solifenacin 5 mg plus tadalafil 5 mg versus solifenacin 5 mg alone in females with overactive bladder using the Overactive Bladder Symptom Score (OABSS).